Experimental Drug Trains Immune System to Shrink Tumors

John Foxx/Stockbyte/Thinkstock(NEW YORK) -- An experimental cancer drug successfully shrank tumors in patients with different kinds of cancer, including typically hard-to-treat lung cancers, according to a new study. Oncologists said the research was encouraging, but more study was needed to know whether the drug would prolong life for cancer patients.

The study, led by Dr. Suzanne Topalian, was presented today at the Super Bowl of cancer professionals, a meeting of the American Society of Clinical Oncology, and published in the New England Journal of Medicine.

In a small, early phase study, researchers used a drug targeting a portion of the body's immune system, a pathway called PD-1, which usually works to stop the body from fighting cancerous tumors. By shutting down the pathway, the drug stokes the body's immune system to fight tumor cells.

Researchers gave the drug to nearly 240 patients with advanced melanoma, colorectal, prostate, kidney and lung cancers. All the patients had tried up to five other treatments, which failed. After up to two years on the drug, tumors shrank in 26 of 94 patients with melanoma, nine of 33 patients with kidney cancer and 14 of 76 patients with lung cancer.

The drug was not without side effects. About 14 percent of patients in the trial reported conditions such as skin rashes, diarrhea or breathing problems.

Alan Kravitz, 70, took the drug for two years to treat his melanoma, which had been diagnosed in the spring of 2007. He said the drug gave him a sunburn that lasted for two months and some mild fatigue. But the tumors that had spread to his lungs were gone.

"My first CT scans showed that the tumors in my lungs basically disappeared," he said. "It enabled my own immune system to kill the tumors. Quite an amazing drug."

Cancer specialists said the fact that the drug caused tumors to shrink, rather than simply to stop growing, is an important measure of success.

"Traditionally in cancer medicine, a tumor that shrinks is an indication that you're killing the cancer," said Dr. Jay Brooks, chairman of hematology and oncology at Ochsner Health System in Baton Rouge, La.

To see that kind of success against several different kinds of cancer, particularly against melanoma, kidney and lung cancers, which are notoriously unresponsive to many of the usual treatments doctors use to thwart them, was also unusual.

David Grobin, 62, a retired Baltimore police officer, underwent nearly three years of unsuccessful chemotherapy and radiation for his lung cancer before taking the drug in February 2011. Now, he said his tumors hadn't totally disappeared, but they are much smaller than they were.

"How lucky can a person be? This is better than anything that I have had before," Grobin said.

"To see this kind of response in cancers that are so difficult to treat is very encouraging," said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society.

The study did not show whether patients lived longer after taking the drug, but experts said early phases of drug trials typically aren't designed to determine improvements in survival. As scientists study the drug in larger numbers of patients for longer periods of time, the drug's success in prolonging life for cancer patients will become clearer.

Lichtenfeld also noted that early trials of drugs are intended to show whether a drug is safe, and don't usually find impressive numbers of patients who respond to the drug. To see those numbers emerging early in drug trials is encouraging, he said.

The difference in the drug's early success may lie in the approach it takes in delivering targeted cancer therapy. Cancer researchers have been chasing more targeted ways to deliver cancer treatments for decades now, in search of a method more refined than the "slash, burn and poison" approaches available with traditional surgery, radiation and chemotherapy. Usually, targeted therapies hone in on a particular part of the cancer itself – a particular kind of cell or a process vital to a tumor's survival.

The current drug is a different because it targets the body's own immune system, training it to recognize tumor cells as foreign, malicious agents.

"In spite of everything we've done so far with cancer drugs, chemotherapy and the rest, what could be more powerful than having the body's own immune system attack the cancer?" said Dr. Roy Herbst, chief of medical oncology at Yale Cancer Center.

Still, doctors remain cautiously optimistic about the drug's early promise.

"In all new studies, there's usually a lot of optimism and hope, but this should all be tempered with a dose of realism," Brooks said. "What's initially reported may not necessarily pan out with time."